Echocardiographic Reference Ranges of Non-invasive Myocardial Work Indices in Children

Noninvasive Assessment of Myocardial Work in Children

The noninvasive assessment of ventricular function is an ongoing challenge, with new tools and measurements always being considered and tested. The noninvasive assessment of myocardial work via the pressure-strain relationship is one of the newer tools proposed to evaluate ventricular systolic function. However, prior to using any new tool, one should understand its properties, utility, and limitations. In this commentary we focus on the noninvasive assessment of myocardial work via the pressure-strain relationship from a pediatric point of view. We address the current knowledge and limitations and propose future directions to better understand this tool.

Normal Values for Echocardiographic Myocardial Work in a Large Pediatric Population

BACKGROUND

Echocardiographic myocardial work is a new load-independent echocardiographic technique to quantify left ventricle (LV) systolic performance. Our aim was to establish normal values for echocardiographic myocardial work in a large population of healthy children.

METHODS

For all the subjects 4-, 2-, and 3-chamber-view videos were stored. The following parameters were obtained by offline analysis: the global myocardial work (GMW), the global myocardial constructive work (GCW), the global myocardial wasted work (GWW), and the global myocardial work efficiency (GWE). Age, weight, height, heart rate, and body surface area (BSA) were used as independent variables in the statistical analysis.

RESULTS

In all, 516 healthy subjects (age range, 1 day-18 years; median age, 8.2 ± 5.3 years; 55.8% male; body surface area (BSA) range, 0.16 to 2.12 m2) were included. GWI, GCW, and GWW increased with weight, height, and BSA (ρ ranging from 0.635 to 0.226, p all < 0.01); GWI and GCW positively correlated with age (ρ 0.653 and 0.507). After adjusting for BSA differences, females showed higher mean GWI (p = 0.002) and GCW values (p < 0.001), thus Z-score equations for gender have been presented.

CONCLUSIONS

We provided MW values in a large population of healthy pediatric subjects including lower ages. MW values increased with age and body size and, interestingly, were higher in females than in men. These data cover a gap in current nomograms and may serve as a baseline for the evaluation of MW analysis in children with congenital and acquired heart diseases.

Non-Invasive Myocardial Work Indices in Infants Born to Mothers With Diabetes in Pregnancy

BACKGROUND

This study used echocardiography to investigate non-invasive myocardial work (MCW) indices in infants born to mothers with diabetes mellitus (DM) in pregnancy (gestational DM: GDM), including those diagnosed under novel classification criteria and those with pre-existing DM.

METHODS AND RESULTS

This single-centered, retrospective study included 25 infants born to mothers with GDM (termed "infant with GDM"), which was diagnosed by oral glucose tolerance test results during pregnancy or the presence of diabetes before the current pregnancy. We evaluated the relationship between the infant's MCW, such as global constructive work (GCW), global work index (GWI), global work efficiency (GWE), and global wasted work (GWW), and the mother's GDM maximal HbA1c during pregnancy. HbA1c level in GDM significantly negatively correlated with GWI* (r=-0.565) and GCW* (r=-0.641). In infants with GDM, GWI and GCW were significantly higher with <6.5% HbA1c than in those with >6.5% HbA1c GDM; however, the specific-layer global longitudinal strain analyses did not show any significant differences between the groups. The pressure-strain loop in infants with >6.5% HbA1c in GDM tended to be smaller than in those infants with <6.5% HbA1c GDM.

CONCLUSIONS

The hyperglycemic environment of GDM leads to impaired MCW in the infants. MCW is useful for screening for cardiac illnesses among infants with GDM. Appropriate maternal blood glucose management while maintaining HbA1c <6.5% might be beneficial for the cardiac performance of infants with GDM.

Pressure-Strain Loops, a Novel Non-invasive Approach for Assessment of Children with Cardiomyopathy

Non-invasive myocardial work (MW) by left ventricular (LV) pressure-strain loops (PSL) is a novel method for assessing myocardial function while adjusting for afterload, yet pediatric data remain lacking. The aims of this study were to investigate the different patterns of LV PSL and non-invasive MW in pediatric patients with hypertrophic (HCM) and dilated cardiomyopathy (DCM) and their association with exercise tolerance. We included 110 pediatric subjects (mean age, 13 ± 4 years, 35 DCM, 40 HCM, and 35 healthy controls). Standard and speckle-tracking echocardiography were performed. LV PSLs were generated, and global work index (GWI), MW efficiency (GWE), constructive work (GCW), and wasted work (GWW) were compared between groups. Regression analysis was used to assess the influence of ventricular function, dimensions, wall thickness, and wall stress on MW and to predict the association between MW and VO2 max as a surrogate of exercise capacity. Patients with DCM had significantly lower GWI compared to controls (GWI 479.6 ± 263.0 vs 1610.1 ± 211.0, P < 0.005). GWE was significantly reduced in DCM (79.3 ± 7.9 vs 95.2 ± 1.3, P < 0.005) due to significantly reduced GCW and increased GWW. HCM patients had significant reduction in GWI and GWE from normal (1237.7 ± 449.1 vs 1610.1 ± 211.0, P = 0.001 and 89.6 ± 4.9 vs 95.2 ± 1.3, P < 0.005, respectively), although less severe than with DCM. In a multivariate regression analysis, GWE had the highest association with VO2 max in both cohorts (DCM: β = 0.68, P = 0.001, HCM: β = 0.71, P = 0.007). Non-invasively assessed myocardial work and LV PSLs provide novel insights into the mechanisms of dysfunction in pediatric patients with cardiomyopathy with good prediction of clinical status and thus hold promise to further explore myocardial mechanistic with clinical relevance in different disease entities.

Changes in myocardial work associated with pediatric kidney transplantation: A pilot study of short-term postoperative effect

The study was mainly to evaluate the changes of left ventricular (LV) myocardial work (MW) in children with CKD stage 5 within 3 months after kidney transplantation (KTx). Forty-three successful KTx recipients (mean age 10.6 years, 58% male) in childhood and 28 healthy children were enrolled. General clinical characteristics and laboratory parameters were collected. Cardiac structure, function, and LV MW were assessed by echocardiography before and after KTx. The results showed that significantly improvement was observed in LV global MW index (GWI), constructive MW (GCW), and wasted MW (GWW) (p < .01), but not in MW efficiency (GWE) and global longitudinal strain (GLS) (p > .05). Besides, blood pressure (BP), renal graft function, LV ejection fraction (LVEF), and LV mass index (LVMi) had obviously improved after KTx (p < .05). Nevertheless, compared with healthy children, higher BP, LVMi, GWW, more deteriorated LV diastolic function and lower GWE were still observed in patients after KTx. The ratio of dialysis duration to CKD course were negatively correlated with the improvements of GWE (p = .004), GWI (p = .01), and GCW (p = .01). In conclusion, a portion of LV MW parameters were obviously improved in children received KTx. Thus, LV MW was superior to GLS in evaluating LV systolic function recovery in these patients. Those patients with insignificant MW improvement should be closely monitored, and adjusted the treatment strategies timely to avoid serious and irreversible myocardial injury after KTx.

Echocardiographic Reference Ranges of Non-Invasive Myocardial Work Indices in Newborns

Background: Myocardial work (MCW), estimated using non-invasive pressure-strain loops, is a novel approach for assessing left ventricular function. MCW offers potential advantages over left ventricular ejection fraction and global longitudinal strain (GLS). This study aimed to establish a reference range for MCW in newborns.

Methods and Results: Overall, 113 healthy newborns (mean [±SD] birth weight 3,120±378 g) were included in the study. After entering peripheral systolic and diastolic blood pressure (BP) values, global constructive work (GCW), global work index (GWI), global work efficiency (GWE), and global wasted work (GWW) were calculated using EchoPAC software (version 204). Considering a mean [±SD] GLS of −16.3±2.8%, the mean [±SD] GWI, GCW, GWW, and GWE was 698.7±147.9 mmHg%, 1,008.5±200.1 mmHg%, 58.1±28.1 mmHg%, and 93.1±2.9%, respectively. All MCW parameters in newborns were lower than those previously reported in children and adults. However, GWI and GCW were more closely correlated with BP and GLS, as in adulthood and children. Estimation of the correlation between MCW and the frame rate index revealed no significant correlations among MCW parameters.

Conclusions: Cardiac function in newborns was evaluated by assessing MCW. With the establishment of reference ranges and normative MCW data for newborns, routine clinical use and rotational mechanics are likely to become increasingly common. Future studies are needed to determine whether MCW is useful in screening for cardiac illness among newborns.

Myocardial work: the analytical methodology and clinical utilities

The evaluation of left ventricular (LV) systolic function is an essential part of the clinical practice of cardiology. Although left ventricular ejection fraction (LVEF) is the most validated and widely used parameter, it has fundamental limitations. LV strain is more sensitive to detect subtle myocardial dysfunction when LVEF was preserved, but it is load-dependent. Invasive left ventricular pressure-volume loop (LV-PVL) is the reliable standard to evaluate cardiac function, but its wide clinical application is limited by the risk of invasive LV pressure detection. Until the advent of non-invasive LV pressure-strain loop (LV-PSL), things have changed. LV-PSL is in good agreement with regional myocardial oxygen consumption and metabolism. Compared with traditional echocardiographic parameters or LV strain, myocardial work (MW) derived from LV-PSL is a more advanced tool that combines deformation as well as hemodynamics through integration of global longitudinal strain and non-invasive LV systolic pressure. In recent years, researches on MW are going on in full swing and show many advantages of MW. This review described the method and discussed the applications, advantages, limitations, and prospects of MW in multiple cardiovascular diseases. The goal is to provide the readers new insights for evaluating LV systolic function and promote the incorporation of MW into daily practice.

Echocardiographic myocardial work in pre-adolescent male basketball players: a comparison with cardiopulmonary exercise test-derived aerobic capacity

Background: Pressure-strain loop (PSL) analysis provides a novel, less load-dependent non-invasive method to quantify myocardial work and demonstrates a significant correlation with the contractile reserve in adult athletes. We aim to validate PSL-derived markers in characterizing LV function in pre-adolescent basketball players by comparing results before and after the cardiopulmonary exercise test (CPX) and explore its association with CPX-derived aerobic capacity.

Methods: Cardiac morphology and function in 20 pre-adolescent basketball players were assessed at 9.7 years old (9.7 ± 1.1 year) before and after cardiopulmonary exercise testing. Echocardiography was performed in all subjects, including two-dimensional speckle-tracking echocardiography (STE). Simultaneous brachial-cuff-measured blood pressure was recorded to perform PSL analysis.

Results: Nineteen subjects were included in the final analysis. Exercise training in pre-adolescent males was associated with lower global work index (GWI) and global work efficiency (GWE) at rest. GWE at stress was significantly correlated with VO2max and peak O2 pulse (p = 0.0122, r = 0.56; p = 0.00122, r = 0.69, respectively). When indexed by body mass, GWI and GWE both significantly correlated with relative VO2max (p = 0.0086 and 0.0011 respectively, r = 0.58 and 0.69 respectively); GWI and GWE at baseline and stress were all significantly correlated with peak O2 pulse (GWI at baseline, p&lt; 0.0001, r = −0.90; GWE at baseline, p&lt; 0.0001, r = −0.89; GWI at stress, p= 0.0289, r = −0.50; GWE at stress, p&lt; 0.0001, r = −0.83).

Conclusion: PSL-analysis-derived GWI and GWE at rest indexed by body mass are associated with cardiopulmonary exercise test-derived peak oxygen consumption and oxygen pulse in pre-adolescent athletes.

Decreased Global Myocardial Work Efficiency Correlates with Coronary Vasculopathy in Pediatric Heart Transplant Patients

Coronary angiography remains the standard for diagnosis of cardiac transplant vasculopathy (CAV), but it is invasive. Non-invasively derived left ventricle (LV) global myocardial work (GMW) indices have not been evaluated. We aimed to assess for correlations between LV GMW and the presence of CAV in a pediatric population. 24 heart transplant patients and 24 normal controls were prospectively enrolled. Patients were age-matched into groups with: orthotopic heart transplant and CAV (OHT-CAV; 6 patients, 33% male, mean age 13.5 years [SD 4.2]), orthotopic heart transplant without CAV (OHT; 18 patients, 67% male, mean age 11.1 years [SD 4.8]), and normal healthy controls (42% male, mean age 12.8 years [SD 5.0]). Transplant patients underwent cardiac catheterization with coronary angiography within 3 months of echocardiogram. Post-processing of echocardiograms with speckle-tracking echocardiography and derivation of GMW indices was performed. OHT-CAV patients had decreased global work efficiency (GWE) compared to OHT (mean difference = 7.01 [1.76, 12.25], adjusted p < 0.01). LV global longitudinal strain (GLS) and LV ejection fraction were not different between groups. Both global work index and GWE were decreased in OHT-CAV and OHT when compared to normal controls (OHT-CAV 1311.23 mmHg% vs OHT 1426.22 mmHg% vs controls 1802.81 mmHg%, adjusted p < 0.01; OHT-CAV 83.87% vs. OHT 90.87% vs. controls 95.41%, adjusted p < 0.01). GWE correlated negatively with the presence of CAV (r = - 0.44 [- 0.72, - 0.05]). This pilot study demonstrates decreased GWE correlates with pediatric CAV. This supports the need for further investigation of this promising diagnostic tool.

Reference Values of Noninvasive Myocardial Work Indices Measured by Echocardiography in Healthy Children

BACKGROUD

Noninvasive myocardial work, estimated by left ventricular (LV) pressure-strain loop (PSL), has been introduced for assessing LV myocardial performance. Based on both blood pressure and speckle-tracking derived strain data, noninvasive myocardial work is considered to be less load-dependent than global longitudinal strain (GLS). In some conditions, such as hypertension or aortic coarctation, the increased afterload will affect strain measurements, and myocardial work can serve as a more robust metric.

OBJECTIVE

We prospectively recruited healthy children to explore the relationship between myocardial work indices and body size parameters, and to determine the reference values of noninvasive myocardial work indices in healthy children.

METHODS

183 healthy children (aged 1-18 years, males: 52.5%) were enrolled in the study. Global work index (GWI), global constructive work (GCW), global wasted work (GWW), global work efficiency (GWE), were assessed by LVPSL and compared according to age and sex.

RESULTS

The mean for GWI was 1,448.7 ± 265.0 mm Hg%, 1,859.8 ± 290.7 mm Hg% for GCW, and the median (interquartile range) for GWW was 54.0 (33.0-82.0) mm Hg% and 97.0 (95.0-99.0) % for GWE. male had greater GWI and GCW) than female (1,572.5 ± 250.2 mm Hg% vs. 1,312.2 ± 208.7 mm Hg% and 1,944.3 ± 299.2 mm Hg% vs. 1,766.6 ± 251.5 mm Hg%, respectively, all P < 0.001). GWI and GCW were significantly correlated with baseline parameters, including age, height, weight, BSA, body mass index, heart rate, and blood pressure. After indexed to BSA, GWI (BSA), GCW (BSA) remained significantly negatively correlated with age (P < 0.001).

CONCLUSIONS

we proposed the normal reference values and regression equations for GWI and GCW based on age and BSA in healthy children. This might provide a basis of reference for the evaluation of cardiac function in children with cardiopulmonary disease.

Normal ranges of non-invasive left ventricular myocardial work indices in healthy young people

OBJECTIVES

Echocardiographic global myocardial work (GMW) indices recently emerged to non-invasively evaluate left ventricular (LV) myocardial performance with less load-dependence than LV ejection fraction (LVEF) or global longitudinal strain (GLS). Yet, few data exist on the descriptions of LV GMW indices in young people. We therefore aimed to provide normal reference values of LV GMW in a healthy young cohort, and simultaneously to investigate factors associated with non-invasive GMW indices.

MATERIALS AND METHODS

A total of 155 healthy young people (age 10-24 years, 59% male) underwent transthoracic echocardiography were recruited and further stratified for age groups and divided by gender. Two-dimensional speckle-tracking echocardiography (2D-STE) were performed to determine LV GLS, peak strain dispersion (PSD) and GMW indices, which include global work index (GWI), global constructive work (GCW), global wasted work (GWW), and global work efficiency (GWE). LV peak systolic pressure was assumed to be equal to the systolic brachial artery cuff blood pressure.

RESULTS

Age and gender specific normal ranges for LV GMW indices were presented. On multivariable analysis, GWI and GCW correlated more closely with systolic blood pressure (SBP) than LV GLS, while both GWW and GWE independently correlated with PSD (P < 0.05 for all). There were no associations between any of the GMW indices with age, sex, body mass index, heart rate, left ventricular mass index as well as LV sizes or LVEF. Of noted, LV GMW indices had good intra-observer and inter-observer reproducibility.

CONCLUSION

We reported echocardiographic reference ranges for non-invasive LV GMW indices in a large group of healthy young subjects, which are reproducible and reliable, and thus can be further used when assessing subclinical dysfunction in young people with myocardial diseases.